/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.dubbo.config;

import org.apache.dubbo.common.extension.ExtensionLoader;
import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.registry.support.AbstractRegistryFactory;
import org.apache.dubbo.rpc.Protocol;

import java.util.concurrent.atomic.AtomicBoolean;

/**
 * The shutdown hook thread to do the clean up stuff. This is a singleton in order to ensure there
 * is only one shutdown hook registered. Because {@link ApplicationShutdownHooks} use {@link
 * java.util.IdentityHashMap} to store the shutdown hooks.
 */
public class DubboShutdownHook extends Thread {

  private static final Logger logger = LoggerFactory.getLogger(DubboShutdownHook.class);

  private static final DubboShutdownHook dubboShutdownHook = new DubboShutdownHook(
      "DubboShutdownHook");
  /**
   * Has it already been registered or not?
   */
  private final AtomicBoolean registered = new AtomicBoolean(false);
  /**
   * Has it already been destroyed or not?
   */
  private final AtomicBoolean destroyed = new AtomicBoolean(false);

  private DubboShutdownHook(String name) {
    super(name);
  }

  public static DubboShutdownHook getDubboShutdownHook() {
    return dubboShutdownHook;
  }

  @Override
  public void run() {
    if (logger.isInfoEnabled()) {
      logger.info("Run shutdown hook now.");
    }
    doDestroy();
  }

  /**
   * Register the ShutdownHook
   */
  public void register() {
    if (!registered.get() && registered.compareAndSet(false, true)) {
      Runtime.getRuntime().addShutdownHook(getDubboShutdownHook());
    }
  }

  /**
   * Unregister the ShutdownHook
   */
  public void unregister() {
    if (registered.get() && registered.compareAndSet(true, false)) {
      Runtime.getRuntime().removeShutdownHook(getDubboShutdownHook());
    }
  }

  /**
   * Destroy all the resources, including registries and protocols.
   */
  public void doDestroy() {
    if (!destroyed.compareAndSet(false, true)) {
      return;
    }
    // destroy all the registries
    AbstractRegistryFactory.destroyAll();
    // destroy all the protocols
    destroyProtocols();
  }

  /**
   * Destroy all the protocols.
   */
  private void destroyProtocols() {
    ExtensionLoader<Protocol> loader = ExtensionLoader.getExtensionLoader(Protocol.class);
    for (String protocolName : loader.getLoadedExtensions()) {
      try {
        Protocol protocol = loader.getLoadedExtension(protocolName);
        if (protocol != null) {
          protocol.destroy();
        }
      } catch (Throwable t) {
        logger.warn(t.getMessage(), t);
      }
    }
  }


}
